The present invention relates to a method for preparing sterilized mineral water without any heat-sterilization treatment, the mineral water being preferably free of an antibacterial agent and packaged in a container such as a bottle; a method for producing a container for packaging the mineral water; and the packaged mineral water per se.
There has been a demand for water having good taste and special water originated from various places have been packaged in containers and put on the market in great quantities. Since there is a possibility of propagation or proliferation of bacteria in pumped up, naturally occurring mineral water, there has, in general, been added chlorine to the pumped up mineral water to inhibit the subsequent propagation of bacteria (see Japanese Patent Unexamined Publication (hereinafter referred to as "J.P. Kokai") No. Sho 57-32779). However, it has been believed that if chlorine is added to mineral water, not only the natural taste of mineral water is deteriorated but also harmful substances such as trihalomethane are formed from the residual chlorine. On the other hand, there has been proposed a method in which mineral water is treated with chlorine and then with active carbon, but the natural taste pecuriar to each mineral water is impaired. Sterilization by heating is also an effective means, but the taste peculiar to each mineral water is likewise impaired.
Mineral water of high quality, in particular that having good taste has a high hardness and contains a large amount of carbon dioxide. However, if mineral water having a high hardness is subjected to the foregoing thermal sterilization treatment, components such as Ca and Mg which serve to increase the hardness of water in the form of bicarbonates are converted into carbonates, i.e., water-insoluble calcium or magnesium carbonates and thus precipitated out from the water and as a result, the hardness of water is greatly lowered.
Under such circumstances, there has been a need for the development of a method for preparing packaged mineral water in which pumped up mineral water is packaged in a container such as a bottle without addition of any antibacterial agent and without performing any thermal sterilization treatment and thereby the proliferation of bacteria in the mineral water is effectively prevented.
On the other hand, plastic bottles such as bottles of polyethylene terephthalate (PET) used for packaging mineral water have been generally sterilized by spraying an antibacterial agent such as hydrogen peroxide on the external and internal walls of the bottles. However, this method suffers from problems such that the taste of the contents thereof is impaired and that the residual antibacterial agent is bad for health of the persons who eat or drink the contents since a trace amount of the antibacterial agent remains unremoved on the walls of the bottle.
Thus, various attempts have been directed to the development of solutions of these problems. For instance, J.P. Kokai No. Sho 63-138931 discloses a method which comprises a sterilization-drying process in which an antibacterial agent is sprayed on a container and then hot air is blown onto the container to dry the same and a washing process for removing and washing away the antibacterial agent adhered to the external and internal walls of the container. In addition, J.P. Kokai No. Sho 60-99828 proposes a method comprising the step of spraying a solution of an antibacterial agent and then a washing solution on a container. However, in these methods, a large amount of washing solution is required for completely removing the antibacterial agent and the processes are very complicated.